Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 281130 AAD
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
630 AM CDT THU AUG 28 2014

.DISCUSSION...UPDATED THE MARINE GRIDS/PRODUCTS TO INCREASE WIND
SPEEDS AND HOIST A SMALL CRAFT ADVISORY FOR ALL BUT THE NORTHWEST
GULF ZONE WITH AN INCREASE IN ORGANIZATION OVER THE LAST FEW HOURS
OF THE LOW OFF THE COAST. THIS CONVECTIVE BURST WILL PROBABLY NOT
LAST MUCH BEYOND SUNRISE AND THIS SYSTEM IS NOT EXPECTED TO BECOME
SIGNIFICANTLY STRONGER OR MORE ORGANIZED BUT THE PRESSURE FALLS IT
CREATED WILL PROBABLY BE SUFFICIENT FOR GUSTY WINDS FOR A FEW
HOURS. /68-JGG/

&&

.AVIATION...MVFR CIGS ARE DEVELOPING AT VALLEY TAF SITES AND
SHOULD PERSIST FOR ANOTHER FEW HOURS AS LOW PRESSURE STRENGTHENS
OFF THE COAST. MOISTURE IS IN PLACE FOR SHOWERS AND STORMS TO
DEVELOP LATER THIS MORNING AND THIS AFTERNOON AND ATTEMPTED TO
TIME THE MOST LIKELY WINDOW WITH A TEMPO GROUP. WENT MORE
OPTIMISTIC WITH VFR CONDITIONS UNDER A HIGH OVERCAST BUT
FLUCTUATIONS IN THE INTENSITY OF THE LOW ARE LIKELY AND THAT COULD
BE TOO OPTIMISTIC. ADDITIONALLY CIGS WILL LIKELY FLUCTUATE MORE
THAN NORMAL AS THIS SYSTEM MEANDERS OFF THE COAST. CARRIED A
SHOWERY HIGH OVERCAST TONIGHT WHICH AGAIN IS SOMEWHAT LOWER
CONFIDENCE THAN NORMAL DEPENDING ON THE FINAL INTENSITY AND TRACK
OF THIS SYSTEM.

&&

&&

.MARINE...WITH THE LOW PRESSURE BECOMING SLIGHTLY BETTER ORGANIZED
ISSUED A SMALL CRAFT ADVISORY FOR ALL BUT THE NORTHWEST GULF OF
MEXICO ZONE DUE TO WIND SPEEDS APPROACHING OR BRIEFLY EXCEEDING 20
KNOTS THIS MORNING AND SEAS POSSIBLY BECOMING ROUGHER THROUGH THE
AFTERNOON. /68-JGG/

&&

.PREV DISCUSSION... /ISSUED 536 AM CDT THU AUG 28 2014/

DISCUSSION...NEAR TERM ADJUSTMENT TO LOWER POPS OVER BROOKS AND
KENEDY COUNTY THIS MORNING AS BANDING EAST OF THERE HAS
DISSIPATED. BEST CONVECTIVE BANDING NOW IS ABOUT 45 MILES EAST OF
SOUTH PADRE ISLAND AND THAT APPEARS TO BE FEELING SHEAR AND
KEEPING THE TROUGH/LOW CENTER A LITTLE FURTHER OFFSHORE. NUDGED
THE INCREASE IN POPS FOR THE VALLEY BACK ABOUT AN HOUR BUT GOES
AND AMSU/SSMI PRECIPITABLE WATER ESTIMATES STILL SUPPORT ABUNDANT
COLUMN MOISTURE WHICH SHOULD FIRE THUNDERSTORMS AND SHOWERS ON
AREAS OF LOCALIZED CONVERGENCE LATER THIS MORNING AND THIS
AFTERNOON. IF THE SYSTEM BECOMES MORE ORGANIZED AND STAYS OFFSHORE
SUBSIDENCE FROM THE CONVECTION MAY LIMIT CONVECTIVE POTENTIAL AS
IT DID YESTERDAY...SEE THE INVERSION AT 640MB ON THE 00Z
SOUNDING... BUT LOW MOISTURE AND HEATING SHOULD BE ABLE TO
OVERCOME THIS. /68-JGG/

PREV DISCUSSION... /ISSUED 441 AM CDT THU AUG 28 2014/

SHORT TERM /NOW THROUGH FRIDAY/...
CURRENT PICTURE...

SHOWER AND STORM ACTIVITY IS PICKING UP ABOUT ON SCHEDULE FOR THE
NORMAL DIURNAL MAXIMUM FOR SYSTEMS LIKE THIS. EXPECT AT LEAST A
LITTLE MORE UPTICK THROUGH THE 6 AM HOUR. OVERALL THE SYSTEM REMAINS
HIGHLY DISORGANIZED AND WINDS SPEEDS ARE FALLING AND PRESSURE RISING
A BURST OF CONVECTION THROUGH THE MORNING COULD MAKE IT A LITTLE
MORE ORGANIZED/LARGER MORE INTENSE AREAS OF RAIN BUT OVERALL A WEAK
AND DISORGANIZED CIRCULATION IS EXPECTED TO COME ASHORE OR MEANDER
NEAR THE SHORE EARLY TODAY WITH LITTLE CHANGE IN STRENGTH OR
ORGANIZATION. MUCH HIGHER COLUMN MOISTURE/PRECIPITABLE WATER IS
EVIDENT NEAR THE CORE OF THE SYSTEM AND TO THE EAST...AND EASTERLY
WINDS ONCE THE STORM MOVES ACROSS THE COAST WILL PUMP IN ABUNDANT
MOISTURE THAT WILL KEEP RAIN CHANCES FAIRLY HIGH THROUGH THE NEXT
FEW DAYS.

TODAY...
HAZARDS/RAINFALL...
LOCALLY HEAVY RAINFALL FROM THUNDERSTORMS IN THE AFTERNOON. AREAS OF
MODERATE TO LOCALLY HEAVY RAINFALL FROM MORE ORGANIZED BANDS THAT
MOVE ONSHORE IN THE MORNING. WIDESPREAD HEAVY RAIN IS NOT
ANTICIPATED.

FLASH FLOOD GUIDANCE REMAINS VERY HIGH AND WIDESPREAD FLASH FLOODING
IS NOT ANTICIPATED.

BEACH CONDITIONS...
SURF HEIGHTS OF 4 TO 6 FEET WATER LEVELS INCREASING UP TO 2 FEET
ABOVE MEAN LEVEL OF LOW WATER. INCREASING SWELL AND WAVE PERIOD WILL
PRODUCE A HIGH RISK OF RIP CURRENTS.

DETAILS...
EXPECT THAT THE MORE ORGANIZED BANDS WILL MOVE ONSHORE WITH THE
HIGHEST INTENSITY/COVERAGE OVER BROOKS AND KENEDY
COUNTIES...ALTHOUGH CONFIDENCE IS LOW AS TO JUST HOW FAR THEY WILL
MOVE ONSHORE. GOOD LOW CONVERGENCE FROM THE LOW/TROUGHING THOUGH
SHOULD WORK WITH DAYTIME HEATING TO GENERATE SHOWERS AND STORMS IN
THE LATE MORNING TO AFTERNOON. STORM MOTION WILL BE SLOW AND
PRECIPITABLE WATER VALUES WILL BE AROUND 2.2 INCHES SO THUNDERSTORMS
MAY PRODUCE LOCALLY HEAVY RAINFALL. THE CENTER WILL MEANDER AND
POSSIBLY REFORM BACK TO THE SOUTHEAST ALONG THE ELONGATED 850MB
TROUGHING WHICH MAY CONTINUE TO PRODUCE LOCALLY HEAVIER RAINFALL
BANDS. WIND SPEEDS WILL BE LIGHT TO MODERATE OUT OF THE NORTH TO
NORTHEAST INITIALLY SHIFTING TO THE EAST LATE.

TONIGHT...
HAZARDS/RAINFALL...
SCATTERED SHOWERS AND STORMS WILL LIKELY PERSIST IN THE OVERNIGHT
HOURS WITH STORMS PRODUCING LOCALLY HEAVY RAINFALL. WIDESPREAD HEAVY
RAIN IS NOT ANTICIPATED.

BEACH CONDITIONS...
WAVE HEIGHTS SHOULD BEGIN TO COME DOWN IN THE EVENING BUT WILL
LIKELY REMAIN NEAR 3 TO 5 FEET WITH WATER LEVELS SLIGHTLY HIGHER
THAN NORMAL. A HIGH RISK OF RIP CURRENTS WILL CONTINUE.

DETAILS...
LOW LEVEL CONVERGENCE WILL REMAIN HIGH AMID BROAD 850MB TROUGHING
AMID ABUNDANT MOISTURE. ACTIVITY MAY PICK UP AFTER MIDNIGHT IF
ACTIVITY ONSHORE INCREASES AND MOVES ONSHORE BUT KEPT THE POPS IN
THE 30 TO 40 PERCENT RANGE. WINDS WILL BE LIGHT TO MODERATE OUT OF
THE EAST AND BE PUMPING IN MORE MOISTURE. THE BEST RAIN CHANCES
SHOULD BE NEAR THE COAST AND EAST OF HIGHWAY 281.

FRIDAY...
HAZARDS/RAINFALL...
EXPECTING MAINLY LATE MORNING AND PM THUNDERSTORMS WHICH WILL MOVE
SLOWLY AND PRODUCE LOCALLY HEAVY RAINFALL.

BEACH CONDITIONS...
WAVE HEIGHTS WILL REMAIN A LITTLE HIGHER THAN THE SUMMER NORM BUT
SHOULD BE LOWER THAN THURSDAY A HIGH TO MODERATE RISK OF RIP
CURRENTS IS FORECAST DEPENDING ON IF ANY CIRCULATIONS REESTABLISH
OFFSHORE AND KEEP PUMPING IN LARGER SWELL HEIGHTS.

DETAILS...
MOST OF THE SURFACE CYCLONE HAS DISSIPATED LEAVING ONLY BROAD 850MB
TROUGHING AND RESIDUAL 500MB VORTICITY...WHICH IS STRONGER IN THE
ECMWF. WIND FIELD SHOULD BE BASICALLY PERPENDICULAR TO THE COAST
WHICH SHOULD SET UP FOR A GOOD SEABREEZE FRONT WHICH WILL HAVE
ABUNDANT MOISTURE TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
STORMS IN THE LATE MORNING. PRECIPITABLE WATER VALUES WILL REMAIN
VERY HIGH WITH SLOW STORM MOTION VECTORS AND LOCAL HEAVY RAIN AND
FLOODING IS POSSIBLE ESPECIALLY OVER AREAS THAT WILL HAVE
EXPERIENCED HEAVY RAIN IN PREVIOUS HOURS. /68-JGG/

LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...BROAD WEAKNESS
BETWEEN THE RIDGE POSITIONS OVER THE SOUTHEASTERN COASTLINE AND
OVER THE WEST COAST WILL MAINTAIN THE POTENTIAL FOR CONV INTO THIS
UPCOMING WEEKEND. IN ADDITION TO THIS THE REMAINS OF THE SURFACE
LOW NOW LOCATED JUST OFFSHORE OF THE LOWER TX COASTLINE WILL
GRADUALLY DRIFT FURTHER INLAND FRI AND SAT WHICH WILL ALSO
MAINTAIN DECENT SURFACE CONVERGENCE OVER THE REGION. DEEP LAYER
TROPICAL MOISTURE LEVELS WILL ALSO PERSIST INTO EARLY THIS WEEKEND
WITH THE MOISTURE LEVELS STARTING TO DIMINISH INTO SUN AND MON
WHICH ALLOW FOR LESS CONV COVERAGE.

THE NEXT WX PLAYER FOR DEEP SOUTH TX WILL THEN BE A TROPICAL WAVE
WHICH IS EXPECTED TO MOVE OUT OF THE WESTERN CARIB SEA THIS
WEEKEND CROSSING INTO THE SOUTHWESTERN GULF OF MEX ON MONDAY. THIS
SURFACE TROUGH/CLOSED SURFACE LOW WILL THEN CONTINUE MOVING W-WNW
TOWARDS THE MEXICO COASTLINE AS THE 500 MB RIDGE AXIS BUILDS OVER
THE SOUTH CENTRAL PLAINS STATES. ENOUGH DEEPER LAYER TROPICAL
RETURNS TO DEEP SOUTH TX WITH THIS FEATURE TO INCREASE THE
POTENTIAL FOR ADDITIONAL CONV EARLY NEXT WEEK. AS THIS SURFACE
TROUGH/LOW MOVES INLAND OVER NORTHEAST MEXICO AROUND MIDWEEK AND
THE RIDGE AXIS REBUILDS OVER THE REGION THE CONV POTENTIAL WILL
START TO DWINDLE LATER NEXT WEEK AS DRIER AND MORE STABLE AIR
BUILDS BACK IN PLACE.

THE GFS IS MUCH STRONGER WITH THE DEVELOPMENT OF THIS TROPICAL
WAVE MOVING OUT OF THE WESTERN CARIB VERSUS THE ECMWF. HOWEVER
BOTH MODELS ARE IN PRETTY GOOD AGREEMENT IN THE OVERALL TRACK OF
THIS FEATURE INTO NEXT WEEK. SO RESIDENTS OF DEEP SOUTH TEXAS
SHOULD PAY CLOSE ATTENTION TO THE LATEST STATEMENTS AND OUTLOOKS
FROM NHC CONCERNING THIS POTENTIAL TROPICAL FEATURE THROUGHOUT THE
WEEKEND AND INTO NEXT WEEK.

HAVE UPPED THE POPS A BIT IN THE LONGER RANGE PERIOD TO REFLECT
THE INFLUENCE OF BOTH OF THESE TROPICAL SYSTEMS WHICH IS MORE IN
LINE WITH GENERAL BLEND OF THE ECMWF AND THE GFS. FOR TEMPS HAVE
ALSO OPTED FOR A MODEL BLEND BETWEEN THE GFS AND THE ECMWF. EXPECT
A LITTLE BIT OF A TREND TOWARDS SLIGHTLY COOLER TEMPS DUE TO THE
IMPACT OF TROPICAL MOISTURE LEVELS...CLD COVER AND POPS ON THE
DAYTIME HEATING. ALSO THE WEAKENED RIDGE POSITION WILL ALSO ALLOW
FOR LOWERED 1000-500 MB THICKNESS LEVELS.

MARINE...NOW THROUGH FRIDAY...
LOW PRESSURE WILL KEEP SEAS CHURNED UP TO NEAR ADVISORY CONDITIONS
THROUGH THE DAY TODAY WITH WINDS DECREASING SLOWLY THROUGH THE DAY.
AN INCREASE IN SHOWER AND THUNDERSTORM ACTIVITY MAY BRIEFLY INCREASE
LOCAL WIND SPEEDS BUT THEY ARE CURRENTLY FORECAST TO REMAIN BELOW OR
JUST UP TO LOW END EXERCISE CAUTION CONDITIONS. SEAS WILL REMAIN
MODERATE TO NEAR ROUGH THROUGH THURSDAY NIGHT.

FRIDAY NIGHT THROUGH MONDAY...MARINE CONDITIONS IN THE LONGER
RANGE PERIOD WILL DEPEND GREATLY ON THE POTENTIAL DEVELOPMENT OF
THE TROPICAL WAVE NOW STARTING TO MOVE ACROSS THE CARIB SEA. IF
THE STRONGER GFS SOLUTION VERIFIES AFTER THE WAVE EMERGES OUT OVER
THE SOUTHWESTERN GULF OF MEX THEN MUCH MORE ELEVATED WINDS AND
SEAS WILL IMPACT THE LATER CWF PERIODS. HOWEVER...IF THE WEAKER
ECMWF VERIFIES THEN MUCH LESS ELEVATED WINDS AND SEAS CAN BE
EXPECTED DURING THE LATER MARINE PERIODS. FOR NOW WILL LEAN
TOWARDS TO WEAKER ECMWF SOLUTION DUE TO THE CURRENT DISORGANIZED
STATE OF THE TROPICAL WAVE.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR TXZ251-256-257.

GM...SMALL CRAFT ADVISORY UNTIL 5 PM CDT THIS AFTERNOON FOR GMZ150-
     170-175.

&&

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/RGV

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